1. Field
The present invention relates to a tamper evident cap for shipping and storage containers. More specifically, the invention concerns a tamper evident cap constructed and arranged to snap fit onto the opening of a steel drum.
2. Description of the Related Art
Vessels or drums of various sizes and shapes are used commercially to store, ship and dispense various substances. Metals drums, which are typically standardized to capacities of, for example, 15-gallon, 30-gallon and 55-gallon, are commonly used to carry an abundance of liquid products, including oil, petrochemicals, chemicals, solvents, water, and the like.
Drums vessels are constructed of a usually cylindrical sidewall and a flat circular lid and a flat circular bottom. An opening is provided in the vessel or its lid to allow the vessel to be filled and to allow the contents of the vessel to be dispensed. The vessel opening is typically sealed with a removable closure or cap. The cap is typically threaded into the opening and forms a seal to prevent the contents from escaping from the vessel.
Without some type of tamper-evident feature, the closure could be removed at virtually any time, such as during shipping or storage, without being noticed. This would mean that someone could tamper with the drum contents without being discovered. This tampering could include partial removal of the drum contents and/or contamination of the drum contents by a foreign substance. Having a tamper-evident feature provides a desirable enhancement to the plug-flange fitting combination.
There is a growing demand today for vessel closure, which provide a visual indication if the vessel has been opened or tampered with in any way.
In general, the prior art uses a closure plug or cap and a covering device (over cap) having a breakable seal, which must be broken to gain access to the closure plug or cap. Some of these tamper evident closures include a tear band, which prevents removal of the closure until the tear band has been irreversibly severed from the closure cap.
In order to provide an indication of prior access to the contents of the vessel, the prior art also teaches a tamper evident cover may be placed over the cap. Certain existing covers or other closures for this purpose use a tear strip along the skirt of the cover that must be removed to remove the cover. A pull-tab or ring is attached to the tear strip, and when the tab or ring is pulled, the tear strip is torn, and the cover may be removed from the vessel. A torn or missing tear strip evidences prior removal of the cover and possible tampering with the contents of the vessel.
Before the cap can be removed from the opening of the vessel that is sealed by the cap, it is necessary to first separate the skirt from the cap before proceeding with the removal of the cap. Typically, these skirts extend downwardly away from the lower edge of the cap. Inspection of the integrity of the skirt will readily indicate whether unauthorized removal of the cap may have occurred. Such unauthorized removal may be attempted by inserting a fingernail or other suitable implement such as the edge of a screwdriver under the edge of the cap. If such prying is attempted, the skirt usually will break away from the edge of the cap and thus serve as an indication of the tampering.
U.S. Pat. No. 5,875,908, entitled “Bottle Cap” to Witt, et al. discloses a reusable bottle cap with a removable tamper evident tear strip or ring. In the Witt device, a plurality of teeth on the tear strip snap under a shoulder on the neck of a milk bottle so that the cap cannot be removed without first removing the tear strip. The tear strip is separable from the cap by a series of frangible tabs, and the tear strip includes a pull ring. When the pull ring is pulled to remove the tear strip, the tabs are broken in series, and the tear strip is separated from the cap. The tear strip is an open annulus so when it is separated from the cap, it can be removed from the bottleneck.
While this may have represented an improvement over former milk bottle closures such as friction fitted cardboard disks, crimped on aluminum foil caps, or crimped on paper caps, it does not provide a sufficient level of tamper evident security to meet current demands. Although the plurality of teeth of Witt will retain the cap and tear strip to the bottle, it is still possible to bend the individual teeth of the Witt device one at a time and effect removal of the cap without destroying the cap, thereby permitting removal and replacement of the cap without detection.
U.S. Pat. No. 5,944,229, entitled “Drum Valve System with Tamper Evident Cap” to Rokkjaer discloses a tamper evident cap for a drum in which the cap has a ledge that snaps under a capturing surface on the drum. When a frangible strip is pulled, the cap is partially torn, and evidence of removal or possible tampering is provided. However, when the strip is removed, it is still necessary to compress the two severed halves of the cap together to effect release of the ledge from the capturing surface on the drum. With this arrangement, while a secure tamper evident cap is provided, the cap is difficult to install, and even more difficult to remove, requiring specific training of personnel at both the filling and dispensing ends of the shipping or storage cycle of the drum.
Another tamper evident cap for use with a drum is shown in U.S. Pat. No. 5,996,833, entitled “Tamper Evident Dust Cover for a Drum Bung” to Lencioni, et al, and discloses a locking annular ring snaps under a lip formed on a neck of the drum, but must be forced onto the neck with great effort with only two major and two minor slots to allow deformation of the ring to pass over the lip and into locked position.
Finally, U.S. Pat. No. 6,193,921, entitled “Method of Making Container Lid with Tamper Evident Slip Band” to Nelson, discloses a container lid having an integrally formed tamper evident flange. The flange is made of a thin web and includes several rupture sections to evidence tampering.
Notwithstanding the improvements offered by the closure caps disclosed in the above-noted patents, certain of these closure caps suffer from certain disadvantage in that it is possible to pry off the cap and frangible skirt together in one motion without causing any damage or separation of the skirt from the major portion of the cap itself. Additionally, the structure of these caps is such that inadvertent prying off of the cap or separation of the skirt from the remaining portion of the cap may occur when any protruding portion of the skirt is caught by nearby objects.
Another disadvantage presented by the tamper proof covering of the prior art is that the filling house which fills containers with consumable product must perform separate operations, to successively install the closure plug or cap, and then to install the over cap. These separate operations, and the separate handling of these separate parts, necessarily mean substantial expense as compared to merely making the closure alone.
It then becomes important to configure a tamper-evident feature that is reliable, easy to install or assemble, and relatively inexpensive.
It is also important to provide a tamper evident closure with provides a clear, reliable indication of previous removal or tampering yet can be produced in a straight draw mold without cams or slides.
It is also important to provide a tamper evident closure, which does not require the use for extra separate parts (over cap), and at the same time, provides the same protection of a tamper evident over cap.
There is a further need for such a tamper evident closure that is so distorted in removal that it cannot be replaced without providing an easily recognized indication that it has been removed.